Broadly, the invention relates to analysis of a vapor phase sample. More specifically, the invention is directed to analysis of a vapor phase sample in which the sample, at ambient temperature and standard pressure, contains a mixture of condensed and non-condensed components. Such a sample when taken from a process stream or reactor would be in a vapor phase which contains materials which are condensable and non-condensable when cooled to normal room temperature at atmospheric pressure.
In some chemical processes the composition of the process mixture, at ambient temperature and standard pressure, includes a mixture of a non-condensed phase, an aqueous condensed phase, and a condensed organic phase. Ambient temperature means herein the temperature of the area outside of a process reactor or stream, also known as room temperature. An example of such a product is a mixture which contains water, hydrogen, oxides of carbon, aromatic hydrocarbons, and aliphatic hydrocarbons. It is very difficult to achieve reliable on-line analysis of such a mixture, particularly if the aromatic hydrocarbons are polymerizable materials.
The term condensable means herein that the gaseous phase sample condenses to the liquid phase sample at standard temperature and pressure. The term non-condensable means herein that the gaseous phase sample remains in the gaseous phase at standard temperature and pressure.
Heretofore, a vapor phase sample with condensable and non-condensable components including water, aromatic hydrocarbons, aliphatic hydrocarbons, hydrogen and oxides of carbon have been collected by cooling the sample to condense water, aromatic hydrocarbons and some aliphatic hydrocarbons. The water and organic phases formed separately and are analyzed separately. The non-condensable phase is difficult to analyze, because some of the water and aromatics become entrained in the non-condensable gas phase.
While chromatographic separations of the sample have been made in the above-described manner, no attempt has been made to analyze the total sample in the vapor state. In particular, no such method has been presented that is capable of separating and quantitatively detecting these components automatically. Prior art methods of separating complex mixtures make no provision for column switching with multiple detectors at temperatures of about 200.degree. C. In particular, no provision is made for maintaining a uniform flow of carrier gas to the detector to minimize upsets during column switching and to optimize sensitivity.
The present invention provides an apparatus and method for analyzing a sample in the vapor phase. Further, this invention allows samples from a process reactor to be analyzed without manual handling of samples. This allows an accurate indication of the contents of the process stream which results in better control of the process.